Exo70 Protects Against Memory and Synaptic Impairments Following Mild Traumatic Brain Injury

TL;DR

Exo70 helps protect brain function after mild traumatic brain injury by regulating NMDA receptors and reducing oxidative stress effects.

Contribution

This study shows Exo70 overexpression prevents mTBI-induced cognitive and synaptic impairments by modulating NMDAR trafficking.

Findings

Exo70 overexpression prevents cognitive impairment in a mouse model of mTBI.

Exo70 preserves hippocampal synaptic transmission and long-term potentiation after mTBI.

Exo70 maintains synaptic GluN2B-containing NMDARs and downstream signaling in mTBI.

Abstract

Mild traumatic brain injury (mTBI), a leading cause of disability in young adults, often results from external forces that damage the brain. Cellularly, mTBI induces oxidative stress, characterized by excessive reactive oxygen species (ROS) and diminished antioxidant capacity. This redox imbalance disrupts hippocampal glutamatergic transmission and synaptic plasticity, where NMDA receptors (NMDARs) are crucial. The exocyst, a vesicle tethering complex, is implicated in glutamate receptor trafficking. We previously showed that Exo70, a key exocyst subunit, redistributes within synapses and increases its interaction with the NMDAR subunit GluN2B following mTBI, suggesting a role in GluN2B distribution from synaptic to extrasynaptic sites. This study investigated whether Exo70 could mitigate mTBI pathology by modulating NMDAR trafficking under elevated oxidative stress. Using a modified Maryland mTBI mouse model, we overexpressed Exo70 in CA1 pyramidal neurons via lentiviral transduction. Exo70 overexpression prevented mTBI-induced cognitive impairment, assessed by the Morris water maze. Moreover, these mice exhibited basal and NMDAR-dependent hippocampal synaptic transmission comparable to sham animals, preventing mTBI-induced deterioration. Preserved long-term potentiation, abundant synaptic GluN2B-containing NMDARs, and downstream signaling indicated that Exo70 overexpression prevented mTBI-related alterations. Our findings highlight Exo70’s crucial role in NMDAR trafficking, potentially counteracting oxidative stress effects. The exocyst complex may be a critical component of the machinery regulating NMDAR distribution in health and disease, particularly in pathologies featuring oxidative stress and NMDAR dysfunction, like mTBI.

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